1. Field of the Invention
The present invention relates generally to a device for filling and/or stabilizing the void within an anatomical organ of the body, particularly within the vasculature, and methods for making and using the device.
2. Description of the Related Art
An aneurysm is an abnormal dilatation of a biological vessel. Aneurysms can alter flow through the affected vessel and often decrease the strength of the vessel wall, thereby increasing the vessel's risk of rupturing at the point of dilation or weakening. FIG. 1 illustrates an abdominal aorta 2 with a sacular aneurysm 4 having an aneurysm wall 6. FIG. 2 illustrates the abdominal aorta 2 with a vascular prosthesis 8 implanted to treat the aneurysm 4, a common aneurysm therapy. Vascular grafts and stent-grafts (e.g., ANEURX® Stent Graft System from Medtronic AVE, Inc., Santa Rosa, Calif.) are examples of vascular prostheses used to treat aneurysms by reconstructing the damaged vessel.
With the prosthesis 8 implanted, an aneurysm sac 10 is defined by the volume between the prosthesis 8 and the aneurysm wall 6. The sac 10 is often filled, partially or completely, with thrombi 12. The thrombi 12 can be partially removed prior to deploying the prosthesis 8. Whether the thrombi 12 are removed, gaps exist between the remaining thrombi 12 or the aneurysm wall 6 and the prosthesis 8, and even when thrombus is present, it can be soft and non-structural. The prosthesis 8 can dislodge or migrate due to the poor fit caused by these gaps and shrinkage of the sac 10 that occurs after the implantation of the prosthesis 8, either acutely due to sizing issues, or over time due to reformation of the sac 10. To reduce the risk of prosthesis dislodgement and migration, the sac 10 can be filled to stabilize the anatomy adjacent to the prosthesis 8 resulting in better efficacy of the prosthetic treatment.
A sac filler, or stabilizer, can be introduced to the sac 10 by trans-graft, trans-collateral, trans-sac, or endoluminal procedures. The trans-graft procedure introduces the sac filler through an opening in the prosthesis 8, as shown by arrows 12. The trans-collateral procedure, shown by arrows 16, introduces the sac filler through a collateral vessel 18 under fluoroscopic guidance that is in direct communication with the sac 10. The trans-sac procedure, often performed laparoscopically, introduces the sac filler through a puncture in the wall 6 of the aneurysm, as shown by arrows 20. The endoluminal procedure introduces the sac filler through the vessel that has the aneurysm 4, as shown by arrows 22, but within the space between the prosthesis and the vessel wall. The trans-graft, trans-collateral and endoluminal procedures are often performed as minimally invasive, entirely endovascular procedures.
It is desirable for a stabilizing element or sac filler to conform to the available space within the sac 10 by operation of the geometry of the device (e.g., by nesting or coiling) and/or by any coatings or materials utilized to promote fusing or other coagulative effect.
U.S. Pat. No. 6,146,373 to Cragg et al. discloses a catheter system and method for injecting a liquid embolic composition and a solidification agent directly into a sac. Cragg et al. teach the use of organic solvents such as DMSO, ethanol and others injected directly in the aneurysm. Cragg et al. teach that these solvents can be toxic to tissue and may cause vascular spasms. Using liquid-solidifying agents in active vessels also carries a high risk that the agents will flow downstream creating emboli or flow into collateral vessels (e.g., lumbar arteries), which may lead to paralysis or other adverse events.
U.S. Pat. No. 4,994,069 to Ritchart et al., U.S. Pat. No. 5,133,731 to Butler et al., U.S. Pat. No. 5,226,911 to Chee et al., and U.S. Pat. No. 5,312,415 to Palermo disclose examples of thrombogenic microcoils, common aneurysm treatments. The microcoil must be tightly packed into the aneurysm to minimize shifting of the microcoils. Shifting of the microcoil can lead to recanalization of the aneurysm. Another disadvantage of microcoils is that they are not easily retrievable. If a coil migrates out of the aneurysm, a second procedure to retrieve the coil and move the coil back into place, or replace the coil, might be necessary.
U.S. Pat. Nos. 6,238,403 and 6,299,619, both to Greene, Jr. et al., disclose an embolic device with expansible elements and methods for embolizing a target vascular site with the device. The device taught by Greene Jr. includes a plurality of highly-expansible elements disposed at spaced intervals along a filamentous carrier. The expansion of the device after deployment reduces the volumetric precision with which the sac can be filled. If the volume of the expanded device is too large, the device can press against the inner side of weakened aneurysm wall and outer side of prosthesis, altering flow within the prosthesis and increasing the risk of rupture of the aneurysm. If the volume of the expanded device is too small, the prosthesis can still alter its position and dislodge or migrate.
There is thus a need for a device and method that can precisely occlude a known sac volume with minimal displacement of the device over time. There is also a need for a device that can be deployed to the sac 10 while simultaneously minimizing toxicity, embolism risk, and other disadvantages previously associated with existing aneurysm sac fillers.